Multi-objective optimization of a supersonic condensation and deposition chamber for cleaner dehydration in CO2 pipeline transport

With the intensification of global warming, carbon capture, utilization, and storage (CCUS) technology has become a key measure to combat climate change, and CO2 pipeline transport is the mainstream method for carbon transport. However, CO2 often contains moisture during transport, which can pose significant risks to pipeline systems. Therefore, employing a supersonic condensation and deposition chamber (SCDC) for dehydration is an effective measure to ensure safe transport. Based on the SCDC, a CO2 dehydration process system for pipeline transportation pretreatment was established. To improve the dehydration performance of the system, this research utilized surrogate model integrated with non-dominated sorting Genetic Algorithm-II (NSGA-II) to achieve multi-objective optimization of the SCDC’s structure. Quadratic and Radial Basis Function (RBF) models were used as surrogates, and the fundamental data were obtained using a computational fluid dynamics (CFD) model that accounts for homogeneous condensation and the coupling of gas, droplets, and liquid film fields. The results show that the RBF model exhibits higher accuracy and optimization performance, with the maximum relative errors between simulated and calculated values being 5.5% for pressure loss rate and 4.2% for overall separation efficiency. A more detailed sensitivity analysis was conducted based on the established RBF model, revealing that the diameter of the divergent section inner body has the greatest influence on the overall separation efficiency. The optimized structure demonstrated a notable enhancement of up to 12% in overall separation efficiency compared to the original structure, all while preserving an equivalent pressure loss rate. Compared to traditional processes, the CO2 dehydration process system based on SCDC saves at least $287,568 annually. For engineering applications, this study introduces the Stokes number similarity criterion to guide the scale up design of the SCDC, so as to maintain the consistency of droplet behavior while increasing the gas processing capacity.